I bought a new Subaru in 2012, began using it for self-employment in 2017, and got rid of the car in 2020.
(I didn't sell the Subaru or trade it in. I just signed over the title to the dealer, and my mother gifted me her used car when she bought a new one.)
From 2017-2020, I deducted the standard mileage rate on my Schedule C. My business use of the Subaru was 45% of its lifetime miles.
In the vehicle section of my 2020 Schedule C, I checked the box that I stopped using the car, wrote the end date, and indicated I converted the car to personal use.
Then, in the section for Sale of Business Property, I entered a Sales Price of $0, calculated the Cost Basis as the FMV for the fifth year of ownership at $9,726, and for Depreciation Taken, I followed the instructions for depreciation recapture and that came to $21,777.
This didn't mess my taxes too much. Does this math and logic make sense to you?
